Surface mounted folding door hardware



Dec. 29, 1964 R. BRYDOLF ETAL 3,162,390

v SURFACE MOUNTED FOLDING DOOR HARDWARE Filed Jan. 23, 1961 2 sheets-sheet 1 F l 1' 42 WW 58 W +44 um 40 5 :-m /5 54 lNl/ENTOES ROBERT BRYDOLF;

COUNC/L A. TUCKER BY THE/R ATTORNEYS HARE/.5, K/ECH, Russzu. & KER/v United States Patent ()fiice 3,162,9i Patented Dec. 29, 1 964 ponents and the door surfaces against which they are seated. With this construction thin particle board doors may be used, which is an important feature.

The door-mounted hardware components engage the rear surfaces of the doors so that they are substantially completely concealed from view.

The invention contemplates, and more specific objects thereof are to provide, a folding door assembly which includes: an overhead track spanning the doorway and carried by the supporting structure in which the doorway is formed; a pair of doors adapted to at least partially span the doorway and adapted to be folded to one side thereof; upper and lower mounting plates mounted on the rear surface of one of the doors adjacent one vertical edge thereof and respectively adjacent the upper and lower ends thereof; upper and lower pivot members respectively carried by the upper and lower mounting plates; means for varying the positions of the upper and lower pivot members vertically relative to the upper and lower mounting plates; otherupper and lower pivot members respectively engageable by the upper and lower pivot members on the upper and lowefinounting plates and respectively carried by the track at the upper end of the corresponding door and by the supporting structure at the lower end of the corresponding door; horizontal adjusting means for horizontally adjusting the upper and lower pivot members mentioned; a guide mounted on the rear surface of the other door adjacent the upper end thereof and adjacent one vertical edge thereof and engaging the track; and hinge means mounted on the rear surfaces of the doors adjacent the other vertical edges thereof and pivotallyinterconnecting the two doors.

Another object of the invention is to provide a mounting plate having a front side seatable against the rear surface of the corresponding door and provided therein with a vertical, forwardly facing first channel in which the corresponding pivot member is vertically movable. A related object is to provide tabs on the front side of the mounting plate which project inwardly from the edges of the first channel therein and which engage the front side of the corresponding pivot member to retain it within the first channel.

A further object is to provide each mounting plate with a vertical, forwardly facing, second channel formed in the rear wall of the first channel, such second channel being located rearwardly of the corresponding pivot member and receiving therein vertically extensible and contractible positioning means for varying the position of the pivot member vertically relative to the mounting plate.

Still another object is to provide a folding door hardware assembly of the foregoing nature wherein the rear wall of the second channel in each mounting plate is provided therein with a horizontal slot intermediate its upper and lower ends, such slot having an element of the corresponding vertically extensible and contractible positioning means seated therein.

An object in connection with one embodiment of the invention is to provide a vertically extensible and contractible positioning means comprising a coil spring having a portion seated in the corresponding slot, the coil spring also being seated against an element on the corresponding pivot member which is in alignment with and disposed within the second channel of the corresponding mounting plate.

An object in connection with another embodiment of the invention is to provide a vertically. extensible and contractible positioning means including a nut seated in the corresponding slot and including a screwthreaded through such nut and extending through an element on the corresponding pivot member which is in alignment with the second channel in the corresponding mounting plate.

A further object of the invention is to provide a horizontally adjustable pivot member, mounted on the supporting structure at the lower end of the pivoted door of the folding door assembly, which is channel-shaped arid telescoped over a horizontal leg of an angle-shaped bracket secured to the supporting structure, this pivot memher having depending flanges provided with inwardlystruck portions under laterally extending flanges of the horizontal leg of the bracket to retain the bracket and the pivot member in assembled relation while permitting horizontal sliding movement of the pivot member along the horizontal leg of the bracket. A related object is to provide a set screw threaded throughthe channel-shaped pivot member and engaging the leg of the bracket to secure the channel-shaped pivot member in any desired horizontal position on the horizontal leg of the bracket.

Another object is to provide an improved means for horizontally adjusting the position of the'pivot member which is horizontally slidable relative to the overhead track.

A further object is to provide pivot members and a guide member on the doors of the folding door assembly respectively having laterally offset pivot and guide elements located substantially in the mid-planes of the doors.

The foregoing objects, advantages, features and results of the present invention, together with various other objects, advantages, featuresand results thereof which will be evident to those skilled in the art in the light of this disclosure, may be attained with the exemplary embodiments of the invention disclosed in detail hereinafter and illustrated in the accompanying drawings, in which:

FIG. 1 is a rear elevational view of a folding door assembly utilizing the surface mounted folding door hardware of the invention;

FIG. 2 is an enlarged elevational view, partially in section, duplicating the circled portion 2 of FIG. 1;

FIG. 3 is a sectional view taken along the arrowed line 3-3 of FIG. 2;

FIG. 4 is an enlarged elevational view, partially in section, duplicating the circled portion 4 of FIG. 1;

FIGS. 5 and 6 are sectional views respectively taken along the arrowed lines 55 and 66 of FIG. 4;

FIG. 7 is an enlarged elevational view, partially in section, duplicating the circled portion 7 of FIG. 1; and

FIG. 8 is a sectional view taken along the arrowed line 8-8 of FIG. 7.

Referring initially to FIG. 1 of the drawings, illustrated therein is a Wall structure 10 provided with a doorway 12 3 4 therethrough which is bounded by aheader 14, .jambs 16 and 18, and a floor 20.

The doorway 12 is adapted to be closed by a pair 22 of doors 2 4 and 26 and a pair 28 of doors 3!) and 32. The door pairs 22 and 28 are identical, except that one is a mirror image of the other, both door pairs being identically hung. Consequently, the description which follows will be restricted to the door pair 28 as a matter of convenience. I

It will be understood that the door pairs'22 and 28, when closed, may be aligned by any suitable folding door aligners. No such door aligners are shown in the drawings as a matter of convenience.

Considering the door pair 28, the doors 30 and 32 thereof are hinged together along their adjacent vertical edge by ordinary flat back hinges34 which aremounted on the rear surfaces of the doors in vertical alignment. With this construction, the hinges 34 are readily attached to the doors 30 and 32 by simple screws and the interdoor hinge axis isrearwardly oifset from the central vertical planes of the doors. As will become apparent, thisrearward oifset of the interdoor hinge axis provided by the hinges 34 produces a toggle joint which moves over center as the doors are closed, thereby holding them in their closed positions.

As shown in FIGS. 1 to of the drawings, spanning the doorway lzand secured to the header 14 thereof, as by screws 36, is an overhead track 38. This track includes two laterally spaced, parallel, depending flanges 49 connected by a transverse web means 42 and cooperating therewith to form below the web means a downwardly facing primary track 44 which is generally channelshaped. The web means 42 is formed to provide a downwardly facing C-shaped, secondary track 46 which is located above the primary track and which openly communicates therewith through a mouth 43 of reduced width formed in the web means. The heads of the screws 36 for mounting the track 38 are contained Within the secondary track 46.

The lead door 32 of the door pair 28 is provided at its upper end, and adjacent the vertical edge thereof opposite the edge to which the interdoor hinges 34 are connected, with a guide meansSt) engageable with the primary track 44. The guide means '50 comprises a mounting plate 52 having a front side seated against the rear surface of the lead door 32. The mounting plate 52 is provided at its upper end with a horizontal flange 54 overlying the upper end of the lead door. Extending upwardly from the flange 54 is a journal 56 for a guide roller 58 engageable with the track flanges 40 defining the primary track 44. The axis of rotation of the guide roller SSlies substantially in the mid-plane of the lead door 32. The mounting plate 52 is provided therein with vertical slots llthrough which extend screws 62 for attaching the mounting plate tothe rear surface of the lead door 32. As will be apparent, this construction permits adjusting the positon of the guide roller 58 vertically to locate itat'the proper level within the primary track 44. v

The anchor door 30 of the pair 28 is pivotally connected to the wall structure adjacent the vertical edge of this door opposite the vertical edge thereof which is connected to the lead door 32 by the hinges 34. Upper and lOWer pivot means 64 and 66 pivotally connect the anchor door 30 to the wall structure 150 Referring to FIGS. 4 to 6 of the drawings, the upper pivot means 64 includes a pivot member 68 having thereon a pivot element in the form of a soclget 70. The pivot means 64 also includesa pivot member 72 having thereon a pivot element in the form of a pin 74 disposed in the socket 761'. The pivot member 68 is mounted on and is horizontally adjustable relative to the track 38, while the pivot member 72 is mounted on and is vertically adjustable relative to the anchor door 30. The common axis of the socket 70 and the pin 74 lies substantially inthemidplaneof the anchor door 30'.

As shown in FIGS. '7 and thelower pivot means 66 includes a pivot member 76 having thereon a pivot element in the form of a socket 73, the pivot member 76 being horizontally adjustable relative to the wall structure common axis of the socket 78 and the pin 82 is substanpivot member. The upstandingportion '86 terminates in "tially in the mid-plane of the anchor door 39 and is substantially vertically aligned "with the common axis of the upper socket 70 and pin 74. I

Since the pivot axis of the anchor door 30 and the guide axis of the lead door 32 lie substantially in the central. planes of the doors, and 'since'th'e interdoor hinge axis provided by thehinges 34 is 'rearwardly offset from the central planes of the doors, the interdoor hinge axis must move over center relative to the plane containing the pivot axis of the anchor door '30 and the guide axis of the lead door 32 as these doors are moved into their closed positions. This provides the hereinbefore discussed toggle joint for assisting in maintaining the doors 3tland32 in their closed positions. 7

Considering the'upper pivot means 64 in more detail with reference'to FIGS. '4' to 6 ofthe drawings, the pivot member 68 is an upwardly facing, channel-shaped memher having the Socket 70 formed in its bottom wall. The pivot member 68 is slidably disposed in the primary track 44 and is provided with transversely spaced, upstanding flanges 84 the upper edges of which are seated against'the under side of the web means 42. The tpivot member 68 is provided at the end thereof opposite the socket 70 with an upstanding portion 86 which includes a doubled-back portion 88 spaced upwardly from thebottom wall of this a tab 90' whichextends upwardly into and is guided by the mouth 48 interconnecting the primary and secondary tracks 44 and 46.

' Within thesecondary tra'ck46 is a nut 2 which'exte'nds downwardly through the mouth 48 and is seated on the doubled-back portion '88 of the upstanding portion 86 of the pivot member 68 is engagement with the tab 90.

screw 94 extends upwardly through the bottom Wall of the pivot member 68 and through the double'd ba'ck portion 88 thereof into threaded engagement with the nut 92, the latter having a square 'or rectangular portion in the mouth -48 to prevent :rotation thereof.

As will be apparent, by loosening. and subsequently tightening the screw 94, the pivot member 68 may he adjusted -horiz ontally of the track 38 to locate the common axis of the socket 70 and the pin '74 at the proper point to mount the-door ,pair :28 correctly. The pa'rticular described structure'o'f the pivot member 68 provides astable anchor for the pivot pin 74 which may be locked in any desirable horizontal position readily by means of V the single screw 94.

The ;pivot member 72 "on the door 30 includes a depending portion 96 adjacent the rear surface of the do'or 30 and a forwardly extending flange 98 overlying the 'upperend of the door hi) and carrying "the pivot pin7'4. The ;piv'ot member 72 is connected to the "door 30 by a mounting ;plate 100 having a front'side "sealed against 'th'e rear :surface of the door 30. At its upper-edge, the

mounting plate 100 is :provided with forwardly-extending tabs $02 which overlie the upper end of the 'door 30 and which serve to position the mounting plate relative tothe door. The mounting'plate is secured to the rear surface of the'door 30 by screws T64;

The mounting plate I00 is provided in its front" side with a vertical, forwardly facing, first channel 10 6 which extends substantially from'the upper-end ofthe ni'ounting plate to the lower end thereof, and in whichthe depend ing portion 96 of the pivot merriber 72 is vertically slid able, and which forms a stable vertical track therefor. The front side of them'ounting plate 10% is provided with tabs 108 thereon which project inwardly'from the-edges of the first channel 106 and which engage the front sides of vertical flanges 110 along the edges of the depending portion 96 of the pivot member 72 to retain this pivot member within the first channel 106 in the mounting plate 100.

The mounting plate 100 is provided in the rear wall of the first channel 106 therein with a vertical, forwardly facing, second channel 112 having a horizontal slot 114 therein intermediate its upper and lower ends. Within the second channel 112 is a vertically extensible and contractible positioning means for varying the vertical position of the pivot member 72 relative to the mounting plate 108, which comprises a vertical, coiled compression spring 116 having at its lower end an enlarged portion 118 disposed in and seated in the slot 114. As will be apparent, the enlarged portion 118 of the spring 116 may be snapped into the slot 114, which acts to key the spring in place. The upper end of the spring 116 is seated against a tab 120 on the pivot member 72, the tab 120 projecting rearwardly into the second channel 112. As will be apparent, the spring 116 biases the pivot member '72 upwardly, upward movement of this pivot member relative to the mounting plate 100 being limited by engagement of a rearwardly extending, hook-like projection pivot socket 70 to facilitate installation of and/ or removal of the doors 30 and 32.

Turning now to a more detailed consideration of the lower pivot means 66, and referring to FIGS. 7 and 8 of the drawings, the pivot member 76 has the general form of an inverted channel telescoped over and horizontally slidable relative to a horizontal leg 124 of an angle-shaped bracket 126 provided with a vertical leg 128 screwed, or otherwise secured, to the jamb 18. The horizontal leg 124 of the bracket'126 has a central portion 130 seated on the floor 20 and has on opposite sides of the central portion thereof laterally spaced, laterally outwardly projecting, longitudinally extending edges or flanges 132 disposed above the floor. The channel-shaped pivot member 76 hasdepending flanges 134 which receive the horizontal leg 124 of the bracket 126 therebetween,

and which have inwardly struck portions 136 projecting laterally inwardly under the longitudinally extending flanges 132 to retain the horizontal leg of the bracket Within the channel-shaped pivot member 76. A set screw 138 is threaded through the upper wall of the channelshaped pivot member 76 and engages the central portion 130 of the horizontal leg 124 of the bracket 126 to secure the pivot member in question in any desired horizontal position so as to properly locate the common vertical pivot axis of the socket 78 and the pin 82.

Considering the pivot member 80, it includes a forwardly extending flange 140 which underlies the door 30 and which carries the pivot pin 82, the latter being located substantially in the mid-plane of the door 30, as herein- .before discussed. The pivot member 80 also includes an upstanding portion 142 which is vertically movable in a vertical, forwardly facing, first channel 144 in a mounting plate 146. This mounting plate is identical to the thereon with tabs 152 which project'inwardly from the edges of the first channel 144 therein and which engage the front sides of vertical flanges 154 alongopposite edges 1 of the upstanding portion 142 of the pivot member 80 to retain such pivot member within-the first channel 144 in the mounting plate 146. As will be apparent, the first channel 144 extends substantially from the lower end of the mounting plate 146 to the upper end thereof, to form a stable vertical track for the upstanding portion 142 of the pivot member 80.

Rearwardly of the first channel 144, and formed in the rear Wall thereof, is a vertical, forwardly facing, second channel 156 having a horizontal slot 158 therein intermediate its upper and lower ends. Disposed in and seated in the slot 158 is a nut 160 which is also seated against the rear side of the upstanding portion 142 of the pivot member to prevent rotation of the nut. Threaded through the nut is a screw 162 which extends upwardly through a tab 164 on the upstanding portion 142 of the pivot member 80 and which is provided with a head 166 at its upper end. The tab 164 extends rearwardly from the pivot member 80 and is in vertical alignment with the second channel 156.

The foregoing nut and screw combination, comprising the nut 160 and the screw 162, constitutes a vertically extensible and contractible positioning means for varying the relative vertical positions of the mounting plate 146 and the pivot member 80 to raise or lower the doors 30 and 32 asrequired to properly position them in the doorway 12. i As this is done, the resilient vertically extensible and contractible positioning means of the upper pivot means 64, which is provided by the spring 116, automatically maintains the pivot pin 74 within the pivot socket 70. Thus, the invention permits adjusting the door positions from the bottom, which is an important feature.

It will be noted that the invention does not require a lower guide track in or on the floor, which is an important feature.

Although exemplary embodiments of the invention have been disclosed herein for purposes of illustration, it will be understood that various changes, modifications and substitutions may be incorporated in such embodiments without departing from the spirit of the invention as defined by the claims which follow.

We claim: i

1. In a hardware assembly to be mounted on a rear surface of a door of a folding door assembly, the combination of: a mounting plate having a front side seatable against said rear surface of said door, said front side of said mounting plate having a vertical, forwardly facing, first channel therein which extends substantially the entire distance between the upper and lower ends thereof, said vertical, forwardly facing, second channel which is vertically substantially coextensive with said first channel, said second channel having at least one wall; a pivot member disposed in and movable vertically in said first channel, said pivot member having a vertical pivot element thereon at one end thereof; and vertically extensible and contractible positioning means in said second channel rearwardly of said pivot member and engaging said mounting plate and said pivot member for varying the position of said pivot member vertically relative to said mounting plate, said positioning means' having a lower end seated against a portion of said wall of said second .channel and having an upper end seated against an element on said pivot member in alignment with'said second channel.

vertically substantially coextensive with said first channel, I

said second channel having a rear wall provided with a in and movable vertically in said first channel, said pivot member having a vertical pivot element thereon at one end thereof; and vertically extensible and contractible positioning means in said second channel rearwardly of said lpivot member and engaging said mounting plate and said pivot member for varying theyposition of said pivot mem- 'ber' vertical'ly relative to said mounting plate, said positioning means including an element seated in said slot, and said positioning means engaging an element on said ipivotfmember in alignment with said second channel.

3 .In a hardware assembly to be mounted on a rear surface o'f a door of a folding door-assembly, the combinat'ion of: amounting platehaving a front side seatable against said rear surface of said door, said front side of said mounting plate having a vertical, forwardly facing, first channel therein which extends substantially v theentire distance between the upper and lower ends thereof, said first channel having a rear wall provided therein with a vertical, forwardly facing, second channel which is vertically substantially coeiitensive with said first channel, said second channel having a rear wall provided with a horizontal slot therein intermediate the upper and "lower ends of said second channel; a pivot member disposedin and movable vertically in saidfirst channel, said pivot member having a vertical pivot element thereon at one end thereof; and vertically extensible and contractible positioning means in said second channel 'rearwardly of said pivot member and engaging said mounting plate and said pivot member for varying the position of said pivot member vertically relative to said mounting plate, said positioning means including 'a coil spring having aportion seated in said slot, said coil spring being seated against an element on said pivot member in alignment with and within said-second channel.

4. a hardware assembly to be mounted on a rear surface of a'door of a folding door assembly, the com bination'of: a mounting plate having a front side seatable against said rear surface of said door, saidfront side of said mounting plate having a vertical, forwardly facing, first ch'anrielth'erein which extends substantially the entire distance between the upper and lower ends thereof, said first channel having a rear Wall provided therein with a -vertical, forwardly facing, second "channel which -lS" V 61 li Qa'lly substantiallycoextensive with said first channel, said see-0nd channel having a r'ear wall provided with a horizontal slot therein intermediate the upper and lower ends of said second channel; a pivot memberdisposed in and *movable vertically :in said first'channe'l, said pivot member having a vertical pivot element thereon atfone end thereof; and vertically extensible and c'o'ntractible V positioning means in said second channel rearwardly of said pivot member and engagingsai'd mounting plate and said pivot member for varying the position of said pivot member vertically relative to said mounting plate, said positioning means including a nut seated in said slot and including a'screw threaded'throughsaid nut and extending through and havn'i'g a head seated on an element on said pivot member in alignmentwith said second channel.

'5. In 'a hardware assembly to be mounted on a rear surface of adoor of a folding 'door assembl the combination ofzi'a mounting-plate having a frontside seatable against said rear surface of said door, said front side of said mounting plate having a vertical, forwardly facing, first channel therein which extends substantially the em tire distance between the uppe'rand lower ends thereof, said first channel having a rear Wall provided therein with a vertical, forwardly facing, second channel which is vertically'substantially coextensive with said first channel, said second"channelhavi'nga rear wall provided with a 'horizontal slot therein intermediate the upper and lower ends of said second channel; a pivot member disposed in *nio'vable vertically 'in said "first channel, said pivot member having a vertical pivot element thereon at one end thereof," said mounting plate having tabs thereon which project inwardly from the vertical edges of said first channel forwardly of said rear wall of said first channel and which engage the front side of said pivot member to retain it within said first channel, the rear side of said pivot member engaging said rear wall of said first channel; and vertically extensible and contractible positioning means in said second channel rearwardly of said pivot member and engaging said mounting plate and said pivot member for varying the position of said pivot member vertically relative to said mountin'gplate, said positioning means including an element seated in said slot, and said positioning means engaging an element on said pivot member in alignment with said second channel.

6. In a folding door hardware assembly, the combination of an angle-shaped bracket having a vertical leg and a horizontal leg, the latter being an upwardly-facing channel having transversely spaced, longitudinally extending edges; 21 channel-shaped pivot member having a pivot element and telescoped over said horizontal leg of said bracket, said channel-shaped pivot member having transversely spaced, depending flanges which receive said horizontal leg of said bracket therebetween and which have portions projecting laterally. inwardly under said longitudinally extending edges of said horizontal leg of said bracket to retain saidihorizontal leg of said bracket within said channel-shaped pivot member, said channel-shaped pivot member being slidable horizontally along said horizontal leg of said bracket; and a vertical set screw threaded downwardly through said channel-shaped pivot member and engaging said horizontal leg of said bracket to secure *said channel-shaped pivot member'in any desired horizontal position on said horizontal leg of said bracket.

7, In a folding door hardware assembly, the combina- 35 tion of: a horizontal track member including two spaced,

parallel, depending flanges and transverse web means connecting said flanges and cooperating therewith to form below said web means a downward'ly facing primary track which is generally channel shaped, said web means being generally C-s'haped in cross section and forming agenerally G-shaped secondary track located above and facing in the same direction as said primary .track,'said secondary track having a mouth of reduced width formed in said web means and inter-connecting the interiors of said tracks; an upwardly-facing, channel-shaped pivot member providing a pivot element and slidably disposed in said primary track, saidpivot member having transversely spaced, "upstanding flanges seated against the under side of said web means on opposite sides of said mouth therein, said pivot member having at one end thereof an upstanding portion terminating in a tab extending into said mouth in said web means; a nut slidably disposed in said secondary track and extending downwardly through said mouth into seating engagement with said upstanding portion of said pivot member; and a screw extending upwardly through said pivot member, and said upstanding portion thereof, and threaded through said nut.

8. In a folding door hardware assembly, the combination of: an angle-shaped bracket having a'vertical leg and ahorizontal leg, the latter being an upwardly-facing'channel having transversely spaced, longitudinally extending flanges; a pivot member having a pivot element, said pivot member being a downwardly-facing channel and 65 said bracket, said pivot member having transversely being telescopically connected to said horizontalleg ofin any desired horizontal position relative to said horizontal leg of said bracket.

References Cited by the Examiner UNITED STATES PATENTS 790,524 5/05 Plice 16-104 X 949,076 2/10 Jacobs 16-105 2,804,136 8/57 Ternes et a1. 2,835,359 5/58 Boldt et a1 16-176 X 2,842,795 7/58 Majeske 16-151 X 2,901,036 8/59 Greig 160-206 Capitani 160-118 Owsiak 248-262 Ford 160-206 Hollansworth 16-151 Sterling et a1 16-105 Duban 16176 Majeske 16-105 Migneault et a1. 16-105 X McNinch 16-99 X DONLEY J. STOCKING, Primary Examiner.

JOSEPH D. SEERS, Examiner. 

1. IN A HARDWARE ASSEMBLY TO BE MOUNTED ON A REAR SURFACE OF A DOOR OF A FOLDING DOOR ASSEMBLY, THE COMBINATION OF: A MOUNTING PLATE HAVING A FRONT SIDE SEATABLE AGAINST SAID REAR SURFACE OF SAID DOOR, SAID FRONT SIDE OF SAID MOUNTING PLATE HAVING A VERTICAL, FORWARDLY FACING, FIRST CHANNEL THEREIN WHICH EXTENDS SUBSTANTIALLY THE ENTIRE DISTANCE BETWEEN THE UPPER AND LOWER ENDS THEREOF, SAID FIRST CHANNEL HAVING A REAR WALL PROVIDED THEREIN WITH A VERTICAL, FORWARDLY FACING, SECOND CHANNEL WHICH IS VERTICALLY SUBSTANTIALLY COEXTENSIVE WITH SAID FIRST CHANNEL, SAID SECOND CHANNEL HAVING AT LEAST ONE WALL; A PIVOT MEMBER DISPOSED IN AND MOVABLE VERTICALLY IN SAID FIRST CHANNEL, SAID PIVOT MEMBER HAVING A VERTICAL PIVOT ELEMENT THEREON AT ONE END THEREOF; AND VERTICALLY EXTENSIBLE AND CONTRACTIBLE POSITIONING MEANS IN SAID SECOND CHANNEL REARWARDLY OF SAID PIVOT MEMBER AND ENGAGING SAID MOUNTING PLATE AND SAID PIVOT MEMBER FOR VARYING THE POSITION OF SAID PIVOT MEMBER VERTICALLY RELATIVE TO SAID MOUNTING PLATE, SAID POSITIONING MEANS HAVING A LOWER END SEATED AGAINST A PORTION OF SAID WALL OF SAID SECOND CHANNEL AND HAVING AN UPPER END SEATED AGAINST AN ELEMENT ON SAID PIVOT MEMBER IN ALIGNMENT WITH SAID SECOND CHANNEL. 